A gas turbine engine is a common source of mechanical output either for propulsion requirements or to provide mechanical energy to drive a generator for generating electricity. A typical gas turbine engine comprises at least a compressor, combustion system, and turbine. If the gas turbine is designed for use in generating electricity, a generator is coupled to the shaft of the gas turbine to convert the mechanical energy into electrical generation. Combustion systems provide a region for mixing compressed air and fuel and containing the reaction that occurs when this mixture is introduced to an ignition source. The hot combustion gases are then directed into the turbine, which is coupled to at least the compressor, and optionally a generator.
A fuel supply system feeding a typical combustion system is shown in FIG. 1. A fuel gas supply conduit 10 comprises a main gas pressure regulator 11, which controls the pressure of the fuel supply to the desired level, and a gas control valve 12, which controls the amount of fuel flowing into the supply system. If the combustion system utilizes different stages of fuel nozzles that are to be supplied from the same fuel conduit, then a splitter valve 13 is employed to split the fuel between the downstream circuits as desired by the operator. In the prior art shown in FIG. 1, a primary circuit 14 and secondary circuit 15 are in fluid communication with fuel gas supply conduit 10 by way of splitter valve 13. Additional splitter valves and control valves may be required depending on how the fuel is to be split and controlled as it passes towards the fuel nozzles in the combustion system.
A common issue for both propulsion gas turbine operators and electrical power plant operators is exhaust emissions exiting the engine. Specifically, emission levels of concern are oxides of nitrogen (NOx) and carbon monoxide (CO). Recently, government regulatory agencies have introduced more stringent rules regarding the amount of emissions that can be produced by electrical power plants, thereby requiring power plant operators to upgrade their gas turbine engines to comply with the new regulations, face fines for exceeding pollutant levels, or restrict the amount of time an engine can operate in order to stay within the emissions regulations. As a result of these emissions regulations, gas turbine manufacturers have spent significant time and resources developing new combustion systems to lower polluting emissions. However, these combustion system designs have primarily focused on changes within the existing gas turbine structure in order to improve fuel/air concentrations and mixing or reducing combustion flame temperature in order to lower emissions.
Further reductions to gas turbine emissions are possible when modifications are made with specific regard to the type of fuel used and how it is mixed prior to injection in the combustion chamber. Such changes to fuel type can allow a present combustion system to emit lower levels of emissions without requiring major hardware changes to the combustion system.